1. Field of the Invention
The present invention relates to an optical pickup device used in an optical disk drive. More particularly, the present invention relates to an actuator for an optical pickup of an optical disk drive capable of tilting in a tangential direction of an optical disk and a method thereof.
2. Description of the Related Art
Generally, an optical disk drive (ODD) records and reproduces information by focusing light beams onto an optical recording medium such as a compact disk (CD), and a digital versatile disc (DVD). Various types of optical disk drives are available, such as a compact disc recordable (CD-R) for reproducing information from a CD, a compact disc re-writable (CD-RW) for recording information on a CD and reproducing recorded information, a digital versatile disc recordable (DVD-R) for reproducing information from a DVD, and a digital versatile disc rewritable (DVD-RW) for recording information on a DVD and reproducing recorded information. Such an optical disk drive includes an object lens for focusing light beams onto an optical disk, and an optical pickup actuator for driving the object lens in order for a spot of the light projected from the object lens to trace around a center of a signal track of the optical disk.
FIG. 1 illustrates an actuator for an optical pickup of a conventional optical disk drive.
As shown in FIG. 1, the actuator for the conventional optical pickup is positioned under an optical disk ‘d’ illustrated by a dash-double-dot line, and includes a holder 20 fixed to a base 10, a blade 40 movably supported by the holder 20 through a plurality of wire suspensions 30 connected to the holder 20 and mounting an object lens L thereon, a focusing coil 50 and a tracking coil 60 both disposed on the blade 40 to drive the object lens L in a focusing direction A and a tracking direction B, a magnet 70 for generating a magnetic field interacting with electric currents flowing through the focusing coil 50 and the tracking coil 60, and a yoke 80 for supporting the magnet 70.
The actuator moves the object lens L in the focusing direction A and the tracking direction B by electromagnetic forces generated between the focusing and the tracking coils 50 and 60 and the magnet 70. As an electric current is applied to the focusing coil 50, the electric current of the focusing coil 50 interacts with the magnetic field of the magnet 70 to generate an electromagnetic force. Due to the electromagnetic force, the blade 40 moves in the focusing direction A, and therefore, moves towards or away from the optical disk ‘d’. Accordingly, a light spot of the light projected from the object lens L is focused onto a signal track of the optical disk with a predetermined size. Also, as the electric current is applied to the tracking coil 60, the electric current of the tracking coil 60 interacts with the magnetic field of the magnet 70 to generate an electromagnetic force. Due to the electromagnetic force, the blade 40 moves in the tracking direction B, and therefore, moves towards or away from the center of the optical disk ‘d’. Accordingly, the light spot traces the signal track of the optical disk without deflecting from the correct signal track.
Meanwhile, it is ideal that a recording surface of the optical disk is level. However, the recording surface is often warped in the manufacturing process. Also, since the blade 40 is hung on one end of the wire suspension 30, rolling occurs during the focusing and the tracking operations. Rolling is a phenomenon in which the blade 40 shakes vertically, and mainly includes a radial direction rolling and a tangential direction rolling. The deflection error and the rolling phenomenon results in the distance between the object lens to the optical disk ‘d’ changing and also the light spot to deflect from the signal track.
For compensation, an actuator is required, which is capable of compensating for the error of the radial direction and has been developed and disclosed by the same assignee of this application in U.S. Publication No. 2002150002, dated Oct. 17, 2002, titled “Optical pickup and method of assembling the optical pickup”, the entire contents of which is incorporated herein by reference. In the cited reference, the magnets are arranged to deflect from a centerline of the drive force by a predetermined distance in order for the drive force of the focusing direction to be applied to the blade in a non-symmetric manner.
However, the actuator has a problem in that it cannot compensate for the error when the optical disk deflects in a tangential direction or an error in the tangential direction rolling in the blade 40 as shown in FIG. 2, in which T and M respectively denote a turntable T on which the optical disk ‘d’ is mounted and a motor M for rotating the turntable.